Field of the Invention
The invention relates to a device for receiving a transmission signal and for transmitting an optical beam having an adjustable intensity, wherein the optical beam effects the transmission signal, including a transmitter for transmitting the beam having a controller for setting the intensity, and a receiver for receiving the transmission signal having an analyzer for outputting a threshold signal if the strength of the transmission signal exceeds a predetermined limit value. The invention also relates to a method of using the device.
Such a device is known and is used, for example, in a measuring configuration which carries out measurements in an electrical power distribution installation and includes a corresponding measuring unit that has to be operated at a high electrical potential. The measuring unit is supplied with power through an optical beam. The beam can be fed to the measuring unit for that purpose through an optical waveguide. A transmission signal, which communicates results of measurements of whatever kind, is transmitted as an optical signal, likewise through an optical waveguide, from the measuring unit. In that case, there is no need at all for an electrically conductive connection between a transmitter, which supplies the optical beam serving to supply power, the measuring unit and a correspondingly configured receiver, which receives the transmission signal and passes it on for further evaluation. An optical beam that is considered in that context is, in particular, a laser beam, emitted by a transmitter which is set up correspondingly, for example as a semiconductor laser. The measuring unit correspondingly includes a transmitting and receiving device which, on one hand, receives the optical beam as a power source and, on the other hand, outputs the transmission signal.
It is regularly the case in such a measuring configuration that there is no electrically conductive connection at all between the measuring unit, which is at a high electrical potential, and the remaining parts of the device, that are at normal zero potential. Therefore, it is not easily possible to set an appropriate intensity for the optical beam serving to supply power. As a rule, the setting must be performed manually in that the intensity is adjusted continuously upwards, proceeding from zero, until the measuring unit receives a sufficient amount of power for its transmission signal. Accordingly, it is necessary, when starting up the device, to increase the intensity of the optical beam until a transmission signal having an appropriately high strength, in particular a strength lying above a predetermined limit value, is received.
An additional impediment emerges when a semiconductor laser is used in the transmitter for the optical beam, since the efficiency of a semiconductor laser generally deteriorates due to aging. Therefore, in the course of operation, it is to be expected that the intensity of the optical beam decreases to such an extent that the transceiver can no longer be supplied properly. It has merely been known heretofore to set the intensity of the optical beam manually to a sufficiently high value in order to remedy such a situation.